How do you paint blood and rust?

Filled in small rust spot about the size of a 1 cm dot with good touch up paint, will rust still spread?

• There was a very tiny little spot of rust the shape of a dot and maybe just half a centimeter in dimater on the front part of the hood on my 99 civic. It look liked it was just a small chip that went through the paint and just now started to rust. I used some touch up paint to fill it in and little bit around it (the car is black). Will the spot still get bigger and the rust spot still spread, or by using the touch up paint to fill it in did i now prevent it from spreading? That is, will the new touch up paint act as a protective coat over the rust area?

• Answer:

  It will probably still spread underneat the touchup paint. Any oxygen molecules that can get to the rusted area...even through paint--- will keep the oxidation (rust) process going once it has started. Better to scratch or sand off the touch-up paint and coat the area first with a rust-reformer product like POR-15 or Rust Bullet and then touch-up over that.